While the invention is subject to a wide range of applications, it particularly relates to a package adapted to encase an electronic component. In particular, the package provides enhanced heat transfer from an electronic component that is isolated from the base component of the package.
It is often desirable to electrically isolate an electrical device such as a silicon die from the base component of the package in which the semiconductor die is enclosed. The dies are often biased on the side bonded to the package. If the base component is electrically conductive, i.e. constructed of metal, it may be especially important to isolate the die from the base component in case the base of the package inadvertently contacts the surface, i.e. the circuit board to which it is attached and thereby causing a malfunction, such as a short ciruit. Electrical isolation between the device and the base of the package may be particularly important for discrete devices having high voltage and high power.
An example of an electrical device which is electrically isolated from its package is disclosed in U.S. patent application Ser. No. 26,808 where a semiconductor die attach system includes, in one embodiment, an electrically insulating buffer disposed between the semiconductor die and the base. Thermally conductive materials such as a silver glass die attach material or a silver alloy solder may be employed to attach the buffer to the die and to the base component. At least one of the die attach materials is compliant so as to accommodate the mismatch in the coefficients of thermal expansion between the die and of the base material. The buffer may be constructed of electrically insulating material such as, for example, a ceramic. A ceramic buffer would be resistant to heat transfer. This could partially be overcome by selecting a beryllia ceramic. However, beryllia is expensive and typically requires a metallized surface for bonding to the solder die attach materials. Moreover, to prevent silver migration from the die attach material into the buffer, which could form a conductive bridge across the buffer, the metallization on the buffer is preferably gold. Also, care must be taken to avoid bridging the solder around the edge of the ceramic buffer so as to form a conductive bridge across the buffer. Although a thicker buffer will normally prevent this type of bridging problem, it adds to the cost and increases the heat resistance.
In a conventional metal package, the heat transfer path from the silicon die to the metal base is essentially limited to the size of the die because the resistance to heat transfer from the die to the outer surface of the base is a function of the area provided for heat transfer. Therefore, it would be advantageous to enlarge the interfacial heat transfer surface.
It is an aim of the present invention to provide a package adapted to encase an electronic component which avoids the problems and difficulties encountered by the prior art approaches.
It is a further aim of the present invention to provide a package adapted to encase an electronic component having enhanced heat transfer from the electronic component to the environment external to the package.
It is a yet further aim of the present invention to provide a package adapted to encase an electronic component which is relatively inexpensive to manufacture.